Igniter for internal-combustion engines



April 21, 1953 E. J. OAKES ET AL 2,635,423

IGNITER FOR INTERNAL-COMBUSTION ENGINES F iled Aug. 28, 1950 INVENTOREEZZWQWJJO%$ Patented Apr. 21, 1953 OFFICE IGNITER FORINTERNAL-COMBUSTION ENGINES Edward J. Oakcs and Ralph K. Rothrock, NewOricans, La.

Application August 28, 1950, Serial No. 181,836

10 Claims.

The present invention relates to igniters for in= ternal combustion.engines, and more especially those of the gas turbine type employing anair compressor which supplies air for combustion to a combustion chamberor a set of combustion chambers in which fuel is burned and the burnedor combusted gases are utilized to drive a turbine or to otherwisedevelop useful power.

A primary object of the invention is to provide an igniter for internalcombustion engines which is capable of igniting efficiently and withcertainty the combustible fuel supplied to such an engine.

A more particular object is to provide an igniter for internalcombustion engines of the gas turbine type for eiiiciently igniting thecombustible mixture of fuel and air in the combustion chamber orchambers thereof. A further object of the invention is to provide anigniter for the gas turbine of an airplane, and especially those of thejet propelled type, which will provide efficient and reliable combustionof fuel supplied thereto at very high altitudes and very lowtemperatures.

The preferred embodiments of the invention are shown in the accompanyingdrawing, wherein- Figure 1 is a side elevation, partly in section, of agas turbine power plant for an airplane provided with fuel ignitersaccording to the present invention. 7

Figure 2 is a detail sectional view, on an enlarged scale, of an igniterembodying the present invention.

Figure 3 is a detail view of an igniter provided with means forsupplying a combustible gas and air thereto.

Figure 4 is a detail view, partly in section, showing another form ofigniter embodying the present invention, having means for supplying acombustible gas and air thereto.

Figure 5 is a diagrammatic view showing the form of the are produced bythe igniter.

In the present instance in which the invention is shown applied to a gasturbine power plant for propulsion of an airplane, ill represents thecasing of the plant within which are mounted the rotor l I of an axialflow compressor having rotor blades 12 mounted on its periphery tocooperate with stator blades i3 fixed on the casing, the rotor andstator blades having appropriate pitch to provide a multistage aircompressor of the axial flow type, and [4 represents the rotor of a gasturbine which is connected to the rotor l I of the compressor by acoupling 15 whereby the compressor will bedriven by the turbine, thecompressor and turbine rotors being mounted rotatably and in alinementin the casing b bearings Hi. The turbine rotor carries rows of blades I?which cooperate with stator blades Is in the casing, these rows ofblades of the turbine having appropriate pitch to provide a multistageturbine which is driven by the burned or combusted gases from thecombustion chamber or chambers. The compressorturbine unit may beconnected through appropriate reduction gearing l9 to a propeller 20 forpropelling the airplane, and the turbine may discharge the spentproducts of combustion through an annular passage 2| for jet propulsionof the airplane. Compressed air from the compressor is received in anannular duct 22 which communicates with a combustion chamber 23 whichmay be of annular form and extending around the axis of the unit or maycomprise a set of separate combustion chambers spaced around thecircumference of the unit, the combustion chamber or chambers beingsupplied with fuel, such a kerosine or similar liquid hydrocarbon, froma header or manifold 24 connected to a suitable source of supply, and byjet nozzles 25 connected thereto and extending into the combustionchamber or chambers, and which spray the fuel into the body ofcompressed air from the compressor. The gas turbine unit as shown anddescribed is of a well known type, and its mode of operation is wellknown to those skilled in the art.

The present invention provides an ignlter for igniting the mixture ofair flowing from the compressor and the atomized fuel sprayed into thecombustion chamber or chambers from the jet nozzle or nozzles which willproduce efficient ignition of the mixture, and which will withstand thehigh temperature of the gases burning in the combustion chamber orchambers. The improved ignited, in its preferred form, comprises atubular outer member 38 having a pipe or other suitable connection 3|for the supply of compressed air thereto, and a central electrode 32which is secured in a porcelain or other suitable ceramic high tensioninsulator 33 which has a collar thereon which is clamped against anannular shoulder 34 in the member 30 by a sleeve 35 threaded into theend of said member. The tubular member which forms one electrode, andthe central electrode, are composed of metal, the central electrodebeing preferably composed of a non-mag netic material such as bronze andhaving a terminal 36 for connection thereto of a source of electriccurrent of a potential and current strength such as that hereinafterdescribed, and the tubular member is threaded at one end 3'! forinsertion through the Wall of the casing into the combustion chamber forcompleting the circult for the ignition current which may be grounded onthe casing. The air supply pipe 3! of each igniter is connected to aheader 3S, and the latter is connected by a pipe 4| to receivecompressed air from a booster pump 39 which may be driven by suitablegearing 40 from the propeller reduction gearing i9, and is connected bya pipe 42 to receive compressed air from the duct 22, which may be at apressure of about pounds per square inch, and increases the air pressureto about 52 pounds per square inch in order that the air thus suppliedto the tubular member 33 of each igniter may overcome the pressure inthe combustion chamber, and to flow into the combustion chamber at thedownstream side of the respective fuel jet nozzle in the path of thespray of fuel therefrom. Compressed air is thus supplied at a suitablepressure to each igniter from the header 38 which is supplied from thebooster pump 39.

In operating a gas turbine power plant equipped with igniters embodyingthe present invention, the outer tubular electrode 30 and centralelectrode 32 of each igniter are connected to the respective terminalsof the secondary of a transformer T which is capable of providing anelectric current of a sufliciently high Voltage and amperage to developand sustain a high tension high temperature are between the inner endsof the outer and inner electrodes 30 and 32 and blown beyond the innerends of these electrodes by a current of air flowing through the igniterfrom the supply pipe 3|, the velocity of which air flow may be adjustedby a valve 3la which may be provided in this pipe, so that the arcformed between the outer and inner electrodes is elongated into a loopand i flame-like in form, and extends into the fuel sprayed into thecombustion chamber from the respective jet nozzle, causing instantaneousignition of the atomized fuel.

It has been found that in operating an igniter of this type with a gapof about one-half inch between the central and outer electrodes andthese electrodes supplied with current at about 20,000 volts and 100milliamperes, by adjusting the air current through the outer tubularelectrode, an are A may be blown in the form of a loop beyond theelectrodes to an extent of from 1 to 4 inches and that blue electricaldischarges appear between the legs of the loop, substantially asindicated in Fig. 5. When the volume and velocity of air flow throughthe igniter is adjusted to extend the are about one inch beyond theelectrodes, the temperature in the loop of the arc is about 400 F., andas the air flow through the igniter is increased, the arc is extended toan increased distance beyond the electrodes and appears to increase inthickness or cross-section and to become more dense, and the temperaturewithin the loop of the arc increases until the arc is extended about 4inches beyond the electrodes and the temperature in the loop of the arcreaches l,000 to 1,200 E, when the optimum ignition eificiency appearsto be attained. Increase of air flow through the igniter to furtherextend the are beyond the electrodes results in a drop in temperature inthe loop of the are. Satisfactory ignition of atomized fuel is attainedwhen the electrodes are supplied with current of from 50 to 100milliamperes, the air current through the igniter is adjusted to extendthe are beyond the electrodes to an extent ranging between 1 to 4inches, and the temperature in the loop of the arc ranges between 400and 1,000 F.

When the are produced by passage of the electric current between theelectrodes is blown in its extended, flame-like form, ionization takesplace which results in separation of the elements of the atmosphere,principally nitrogen and oxygen, and under the influence of the heatdeveloped by the current flowing in the arc, nitrogen, nitric oXide andfree oxygen are present in the vicinity of the elongated arc. When thefree oxygen comes into contact with the mixture of oil and air,instantaneous ignition and combustion of the fuel takes place,comparable with the well known phenomena of explosion whenever freeoxygen comes into contact with hydrocarbons in any state.

After the fuel spray from each jet nozzle has been ignited, the supplyof electric current to the igniters may be cut off as the flames fromthe jet nozzles will be sustained under normal conditions by theincoming fuel and compressed air, but the flow of air through thetubular member of the igniter is continued, thereby cooling the igniter,and especially the insulator for the central electrode, from thedestructive effect of the high temperature of the burning gases in thecombustion chamber.

Jet driven airplanes employing a gas turbine power plant operate mostefiiciently at very high altitudes, but it has been found that at suchhigh altitudes where the temperature of the atmosphere may be manydegrees below zero Fahrenheit, the flame in the combustion chamber isliable to become extinguished or fail to burn properly, due probably tothe cooling effect of such very cold air on the flame in the combustionchamber. In order to remedy or relieve such a condition, means may beprovided for the introduction of an inflammable gas through the igniterto be ignited by the arc. Such an inflammable gas as butane or propanemay be stored in a tank 50 and connected to a header 5|, the latterbeing connected by branch pipes 52 with the respective igniters, each ofthe branch pipes being preferably provided with a valve 53 forregulating the supply of such an inflammable gas. As shown in Fig. 3,the branch pipe 52 for the supply of inflammable gas is connected to theair supply pipe 3|, and by appropriately adjusting the valves 3 la and53 an appropriate proportion of the gas to air may be obtained.

Fig. 4 shows a modification in which the pipe 52a for the supply ofinflammable gas is connected, through an electrical insulating sleeve54, to the central electrode 32a which in this instance is hollow ortubular, so that the gas in passing through the hollow electrode willcool it and the surrounding insulator.

In either of the arrangements shown in Figs. 3 and 4, the highlyinflammable supplemental gas supply to the electric are produced betweenthe electrodes of the igniter, when ignited by the arc, provides a veryhot flame which will ignite the fuel sprayed in the combustion chamber,notwithstanding the cooling effect of very cold and rarefied air at highaltitudes to ensure easy starting of combustion of the fuel on which theplant operates, and to overcome or prevent flame failure in thecombustion chamber. Adjustment of the proportion of oxygen toinflammable gas ensures efiicient burning of this supplementalinflammable gas supply, as such gases burn most efficiently when mixedwith an appropriate percentage of oxygen.

The invention is shown applied in the present instance to a conventionaltype of gas turbine power plant for propulsion of aircraft employing anaxial flow compressor which is driven from assume a a gas turbineaxially alined therewith and which takes in air through an annularopening at its forward end and compresses the air and delivers it to anannular combustion chamber or an annular series of combustion chambersin which liquid fuel is sprayed and the sprayed liquid is ignited by anannular series of igniters in the annular combustion chamber or in therespective combustion chambers of the series, but it is to be understoodthat the invention is also applicable to aircraft of the so-calledram-jet type in which the forward speed of the aircraft in flight issufficient to compress the air sufflciently for com- .bustion of thefuel supplied thereto without requiring the use of a comprsseor.

It is also to be understood that although the invention is shown in thepresent instance as applied to a turbine power plant of a conventionaltype in which the power developed is used for driving a propeller at itsforward end and the combusted gases exhausting from the turbine at itsrear end are utilized for jet propulsion, the power plant may be of thetype in .or No. 6 fuel oil (bunker C, 6-16B.), which can not be ignitedby an ordinary spark plug supplied as usual with an electric current offrom 5,000 to 10,000 volts and a current strength of about 20milliamperes, thereby enabling such available and less expensive heaviergrades of oil to be used economically as fuel.

By maintaining flow of a current of air through the igniter duringoperation of the plant, the igniter is cooled and thereby protected fromthe destructive effects of the high temperature of combustion in thecombustion chamber.

We claim:

1. The method of igniting fuel in an internal combustion engine,comprising atomizing the fuel and spraying the atomized fuel in the formof a jet into a current of compressed air to form a flowing current ofcombustible mixture, forming a high tension electric arc in proximity tothe flowing current of combustible mixture, and directing anothercurrent of air against the arc in sufficient volume and velocity toelongate the arc and extend it into the flowing current of combustiblemixture.

2. The method of igniting fuel in a gas turbine plant of the typecomprising a combustion chamber, a compressor for supplying compressedair to said chamber to flow therethrough, means for feeding fuel to thecombustion chamber for combustion therein, and a gas turbine arranged toreceive combusted gases from the combustion chamber, which methodcomprises spraying atomized fuel into the air flowing through thecombustion chamber to form a flowing current of combustible mixture,forming a high tension electric arc in the combustion chamber inproximity to the path of the flowing current of combustible mixture, anddirecting another current of air against the arc in sufficient volumeand velocity in a direction transverse to the current of combustiblemixture to elongate the arc and extend it into the flowing current ofcombustible mixture.

3. The method of igniting fuel in a gas turbine plant of the typecomprising a combustion chamber, a compressor for inducing flow of acurrent of compressed air through the combustion chamber, means forfeeding fuel to the combution chamber for combustion therein, and a gasturbine arranged to receive combusted gases from the combustion chamber,which method comprises spraying atomized fuel into the current of airflowing through the combustion chamber to form a flowing current ofcombustible mixture, producing a high tension electric are betweenelectrodes adjacent to the path of the flowing current of combustiblemixture, and directing another current of air past the electrodes insufficient volume and velocity and in a direction transversely of saidcurrent of combustible mixture to extend the are beyond the electrodesand into the flowing current of combustible mixture.

4. The method of igniting fuel in a gas turbine plant of the typecomprising a combustion chamber, a compressor for supplying a current ofcompressed air to flow through the combustion chamber, means forsupplying fuel to the combustion chamber, and a gas turbine arranged toreceive combusted gases from the combustion chamber, which methodcomprises spraying atomized fuel into the combustion chamber tocontinuing the flow of the current of air past the electrodes.

5. The method of igniting fuel in a gas turbine plant of the typecomprising a combustion chamber, a compressor for inducing flow of acurrent of compressed air through the combustion chamber, means forfeeding fuel to the combustion chamber for combustion therein, and a gasturbine arranged to receive combusted gases from the combustion chamber,which comprises spraying atomized fuel into the current of compressedair fiowing through the combustion chamber to form a flowing current ofcombustible mixture, producing a high tension electric are betweenelectrodes adjacent to the path of the flowing current of combustiblemixture, and directing a current of air at a pressure higher than thatof said current of compressed air past the electrodes in suflicientvolume and velocity to extend the arc beyond the electrodes and into theflowing current of combustible mixture.

6. An igniter for an internal combustion engine having means forproducing a current of air and means for spraying atomized fuel in acombustion chamber to form a flowing current of combustible mixture,comprising electrodes in proximity to the path of the flowing current ofcombustible mixture, means for supplying electric current to theelectrodes sufficient in intensity to produce an electric arc betweenthem and to maintain such are in elongated form, and means for directinga current of air past the electrodes to elongate the arc beyond them and7 into the :fiowing current of combustible mixtur '7. An igniter for a:gas turbine plant of the type having a combustion chamber openat rbOthends, a compressor for applying .a current 01' compressed air 'to one.end :of the .combustion -rent to the electrodes to establishan:electric are between them and to maintain such are in extended relationto the electrodes, and means-for conducting a current of air past theelectrodes in a direction transverse :to the current of combustiblemixture to elongate the arc and extend it from the .electrodes and intothe current of combustible mixture.

8. An igniter for a gas turbine .plant of the type having a combustionchamber open-at both ends and adapted to receive a current of compressedair and a supply 'of fuel to ;form a current of combustible.mixtureforflow through and to discharge from the combustion chamber, comprisingelectrodes .located in a wall of the com- .bustion chamber adjacent tothe path of the current of combustible mixture and downstream from-thejet nozzle, means for supplying anelec- .tric current to the electrodestoproduce anelectrio are between them, and means for conducting .a.current of air at a pressure higher than that ofsaid current ofcompressed'air past the electrodes into the combustion chamber in adirection transverse to the flowing current .of combustible mixture toelongate the arc and extend it into said flowing current of combustiblemixture.

9. A gas turbine power plant comprising a combustion chamber,acompressor for supplying a current of compressed air to said chamber,

:means for spraying fuel in the combustion cham- :ber :to produce acurrent .of combustible mixture for combustion therein, a turbine arraned to receive combusted gases from the combustion chamber and connectedto the compressor :or driving it, a .fuel 'igniter comprising electrodespositioned in a wall of the combustion chamber .a'longwhich the currentof combustible mixture flows, means for supplying an electric current to:the electrodes of .suflicient intensity to produce an electric arebetween the electrodes and "to maintain such an arc in extended relationthereto, means driven by the turbine and separate from the compressorfor compressing air to a pressure higher than the pressure :inthecombus- 'tion chamber, and means for conducting 0, current of suchhigher pressure air past the electrodes to elongate the arc and extendit beyond the electrodes and into the current of combustible .mixture.

10. A .gas turbine power plant as defined in claim-9, wherein said meansfor compressing air to a higher pressure comprises a pump connected toreceive compressed air discharged by said compressor, and is operativeto increase the pressure thereof.

EDWARD J. CAKES. RALPH K. ROTHROCK.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,695,152 Martindale Dec. 11, 1928 1,920,460 Bruns Aug. 1,1933 1,948,663 Irwin Feb. 27, 1934 2,326,072 Seippel Aug. 3, 19.432,465,092 Harkness Mar. 22, 1949 2,493,743 Benson Jan. 10, 19502,581,999 Blatz Jan. 8, 1952 FOREIGN PATENTS Number Name Date 134,368Austria July 25, 19,33

